1. Field of the Invention
The present invention relates to an optical fiber telecommunication cables, and more particularly to optical fiber cables made of optical fiber ribbons and a manufacturing process for the same.
2. Description of the Related Art
Optical fiber cables are widely used in the telecommunications field to transmit information. In general, an optical fiber cable can be classified into a single-core optical fiber cable and a multi-core optical fiber cable depending on the number of housed optical fibers. The multi-core optical fiber can also be classified into optical fiber ribbons and loose tube optical fiber cables.
The former relying on optical fiber ribbons or multi-ribbons achieve optimum packing density in high fiber count cables by coating a plurality of optical fibers side-by-side, parallel to one another and substantially in the same plane. As the plurality of optical fibers is housed in this type of arrangement, optical-fiber ribbon cables achieve high packing density. Thus, the ribbon optical fiber cable is widely used as an optical transfer medium in an optical telecommunication system.
Referring to FIG. 1, the ribbon optical fiber cables 100 according to an embodiment of the conventional art comprise a plurality of optical fibers 110 and ribbon coating layers 120 surrounding the external peripheries of these optical fibers. The conventional ribbon optical fiber cables 100 have a thickness between 0.28 mm and 0.40 mm, and a width of 1.1 mm when the optical fibers with four cores are provided, 2.1 mm when the optical fibers with eight cores are provided, and 3.1 mm when the optical fibers with twelve cores are provided. Furthermore, the conventional ribbon optical fiber cables 100 have a coating thickness of about 30-50 xcexcm on both side surfaces thereof.
The conventional ribbon optical fiber cables 100 described above have some drawbacks in that a gap G is generated between the outermost layers between adjacent ribbonizing layers, which envelops a plurality of fibers in a common plane, and cause problem when being connected to the optical fitting. When the gap G is great, it is difficult to connect the ribbon optical fiber cables 100 to optical fittings. Furthermore, forcing the ribbon optical fiber cables 100 into a connection to the optical fittings while having such a gap G can results in undesirable side pressure or bending load. As a consequence, a bent loss occurs in the housed optical fibers 110.
The present invention relates to a ribbon optical fiber cable, which can minimize a gap among a plurality of ribbon optical fibers when horizontally arranged in a substantially horizontal orientation, and a die unit for coating the ribbon optical fiber.
Accordingly, the present invention provides an optical fiber ribbon structure, a plurality of optical fibers arranged in a horizontal orientation; a coating layer having a upper layer and a lower coating layer covering the upper and lower portions of the optical fibers; and, outermost coating layers coated on outer surfaces of farthest optical fibers from the center of the optical fibers and having a thickness substantially thinner than the upper and lower coating layers.
The present invention provides a dye body having an opening, the dye body having a cross section in a rectangular shape, wherein the height H of the dye opening is defined according to H=D+(0.05xcx9c0.2 mm) and D represents an external diameter of the optical fiber), and wherein the width W of the dye opening is defined according to W=Dxc3x97N+(0xcx9c0.1 mm) and N represents the number of cores of the optical fiber.